An attempt on systematic review

1. Physical activity on improving cognitive
function in Alzheimer’s disease: A
Systematic Review (Attempt)
Chiew Keong John, Ng Jun Quan
Last update: 16 July 2019
Introduction
Alzheimer’s disease (AD) is a
neurodegenerative brain disorder that
progressively decreases cognitive function,
with symptoms including memory difficulties,
language dysfunction, disorientation, and
mood swings. It is the leading cause of
dementia among older adults in the world. (1)
Severe AD often causes complications such as
immobility, malnutrition and even death, with
pneumonia identified as the most common
cause of death among elderly patients with
AD. (2)
With life expectancy trends on the rise, this not
only puts the increasing numbers of elderly
people in ageing populations risk of
developing dementia, but the long duration of
illness before death contributes significantly to
the public health impact because much of that
time is spent in a state of disability and
dependence. With the worldwide economic
cost estimated to be US$818 billion in 2015,
and projected to increase to become more than
a trillion dollars within the decade, dementia is
far from a small issue. (3)
The current underlying principle behind
pharmacologic treatment of AD is the
management of symptoms and is unable to
effectively halt or slow down the deterioration
of neurons and cognitive function, largely due
to the gaps of knowledge about the precise bio-
molecular pathophysiology of AD. (4) In
recent years, non-pharmacologic therapies
have often been used in adjunct with
medication to treat patients with AD, with the
aim of improving physical ability, cognitive
behavioural symptoms and overall quality of
life.
Research into employing exercise programs to
increase physical activity as a form of non-
pharmacologic therapy seems to have
promising results. Multiple studies
encompassing various types and intensities of
physical activity suggest that exercise can have
beneficial effects on cognitive function,
physical ability and ability to perform
activities of daily living (ADLs). (5)(6)(7)
Aerobic exercise refers to the type of moderate
intensity physical activity that can be sustained
for more than just a few minutes, and differs
from anaerobic exercise that is performed at an
intensity sustained for only a few moments. (8)
Previous reviews have focused on physical
activity as a form of non-pharmacological
therapy, but did not specifically focus on
aerobic exercise as an exercise modality.
Further research is thus required to determine
the efficacy of aerobic exercise on improving
cognitive function in patients with AD.
Significance to local context
Locally, according to a study led by the
Institute of Mental Health in 2015, one in 10
people aged 60 and above may have dementia.
This translates to almost 82,000 people in
2018, with the number expected to continue
rising. In terms of economical costs, an

2. estimated S$2.8 billion was spent in 2015, with
this figure expected to rise above S$6 billion
by 2030. (9) Thus great emphasis has to be
placed on improving methods of diagnosis,
interventions and holistic support of AD.
As such, this systematic review aims to assess
the effectiveness of physical exercise as a form
of intervention in improving cognitive
function in patients with AD.
ResearchQuestion
This review seeks to establish, through the
available literature, what is best practice for
smoking cessation. The specific review
question to be addressed are:
1) How effective is aerobic exercise in
improving cognitive function in
existing AD patients?
Inclusion Criteria
Type of Participants:
This review will consider all studies that
involve human subjects of ages 50 and older
who are clinically diagnosis with Alzheimer’s
Disease and have the physical capability to
engage in moderate levels of physical activity.
Types of Interventions:
Interventions of interest included those that
performed specifically aerobic training for a
period of 3 weeks or more.
Types of Outcome Measures:
The primary outcome measure of interest is
cognitive function encompassing any
improvements in reasoning, memory, attention
and language.
Types of Studies:
The review considered all studies evaluating
the effectiveness or efficacy of interventions
relating to improvement of cognitive function
through aerobic exercises. In the absence of
this type of studies, those that evaluate a
combination of aerobic exercises with
flexibility and balance will also be considered.
Search Strategy
The search strategy will be designed to access
published materials and comprises of three
stages:
1) A limited search of Web of Science and
PubMed to identify relevant keywords
contained in the title, abstract and
subject descriptors.
2) Terms identified in this way, and the
synonyms used by respective
databases, will be used in an extensive
search of the literature.
3) Reference lists and bibliographies of
the articles collected from those
identified in stage two above will be
searched.
The initial search terms will be ‘exercise’,
‘cognitive’ and ‘Alzheimer’.
Full copies of articles identified by the search,
and considered to meet the inclusion criteria,
based on their title, abstract and subject
descriptors, will be obtained for data synthesis.
Articles identified through reference list and
bibliographic searches will also be considered
for data collection based on their title.
Results of the Review
Table 1 outlines the selected characteristics of
the 13 studies included in the review. They
were divided into 3 categories based on the
type of exercises performed: (a) aerobic
exercise, (b) aerobic exercise accompanied
with flexibility or balance training, (c) walking
program. 9 studies introduced aerobic
exercises to improve cognitive function in
Alzheimer patients. These studies engaged
their patients in a moderate to high intensity
cardiovascular aerobic exercise that aimed to

3. reach 65-80% of their maximal heart rate.
These exercise sessions were performed 3
times a week for a period between 12-16
weeks. Hernandaz et al., unlike the other
studies which used treadmill, bicycles or cross
trainers, performed aerobic exercise through
dance routines, circuit training as well as motor
developmental exercises. These studies used
the Mini Mental State Exam (MMSE) to
evaluate cognitive function and all 9 studies in
this review showed improvements in their
MMSE scores after the intervention of aerobic
exercise.
Aerobic exercise coupled with flexibility and
balance training was the second type of aerobic
exercise intervention used to improve
cognitive function in Alzheimer patients.
These sessions comprise respiratory exercises,
static and dynamic balance training, gait
circuits with and without obstacles, and
stimulation of activities of daily living and of
fine motor coordination and balance. There are
also sessions of cognitive stimulation which
include reminiscence sessions, and exercises to
improve attention, verbal fluency, and general
recognition. Patients from Arcoverde et al.
showed that physical and cognitive stimulation
in patients with AD may contribute to a less
aggressive progression of the cognitive and
functional status as compared to sedentary AD
patients.
Two studies introduced therapeutic
interventions using a walking program. The
study done by Venturelli et al. showed that
cognitive levels, evaluated by the MMSE test,
remained unchanged during the walking
program with no significant differences for the
Walking Group, while the control group
showed a significant decrease in cognitive
functions after 6 months. The temporary
stabilization of progressive cognitive
dysfunctions shown in the Walking Group
could be attributed to improvements in blood
circulation in the brain and changes in
neurotransmitter synthesis stimulated by the
exercise sessions.
In terms of target groups, all our studies (13)
focused on general adults 50 years and older
that were clinically diagnosed with
Alzheimer’s and can perform moderate to high
intensity physical activity. 6 out of the 12
studies used a Randomized Control Trial to
perform their experiments whilst the rest did a
Cross Sectional Study or Single Group
Repeated Measure Design. The most popular
(7) cognitive measurement test was the Mini
Mental State Examination (MMSE) but other
measures include Symbol Digit Modalities
Test (SDMT), Number Sequencing, Verbal
Test and MOC

5. Moving forward from this research
 Further research into biomolecular mechanisms of dementia, methods of diagnosis and
intervention to improve outcomes.
 Further research into intensity of aerobic exercise needed
o Moderate to higher intensity aerobic exercise suggest more promising results in
improving cognitive function, as compared to walking program
 Smart homes – equipped with sensors, video cameras and other ambient assisted living
technologies
o Gathering data on night-time wandering, falls, physical activity
o Monitor progression of dementia and helps clinician evaluate changing needs of
patient
o Types of sensors in development include: leak and spill detectors, glass break
detectors, door and window sensors, voice activation sensors, gait monitors, fall
detectors, caregiver alarms
 Orthotics – to aid with cognitive, functional or physiological deficits
o Memory aids devices in the from of glasses, clothing badges
o Navigation devices based on standard routes, and corrects navigational errors and
visuospatial deficits

6. Bibliography
1. https://www.who.int/en/news-room/fact-sheets/detail/dementia
2. https://www.ncbi.nlm.nih.gov/pubmed/19170740
3. https://www.alz.co.uk/research/WorldAlzheimerReport2015.pdf
4. https://www.alz.org/media/Documents/alzheimers-facts-and-figures-2019-r.pdf
5. Palleschi L, Vetta F, Gennaro ED, Idone G, SottosantiG, Gianni W, et al. Effect of aerobic training on the
cognitive performance of elderly patients with senile dementia of alzheimer type. Archives of Gerontology and
Geriatrics 1996;22:47–50. doi:10.1016/0167-4943(96)86912-3.
6. Venturelli M, Scarsini R, Schena F. Six-Month Walking Program Changes Cognitive and ADL Performance in
Patients With Alzheimer. American Journal of Alzheimers Disease & Other Dementias 2011;26:381–8.
doi:10.1177/1533317511418956.
7. Borges-Machado F, Ribeiro Ó, Sampaio A, Marques-Aleixo I, Meireles J, Carvalho J. Feasibility and Impact
of a Multicomponent Exercise Intervention in Patients With Alzheimer’s Disease: A Pilot Study. American
Journal of Alzheimers Disease & Other Dementias® 2018;34:95–103. doi:10.1177/1533317518813555.
8. https://www.emedicinehealth.com/aerobic_exercise/article_em.htm
9. https://alz.org.sg/dementia/singapore/